The invention concerns a procedure for the production of electrical energy and/or heating and operational heat by utilizing combustion heat from fossil fuels, dried in an indirectly heated fluidized bed dryer prior to burning, especially of crude lignite. The resultant flue gases are cooled to an interstage temperature in a heat exchange between the working materials and the combustion air, are freed from dust and, if necessary, are freed from other damaging substances and, subsequently, discharged into the atmosphere.
In power plants in which fossil fuels with a high content of moisture are used as, for example, crude brown coal with a water content of 50% or more, a considerable portion, up to 25% of the utilized fuel, must be used for the vaporization of the water which then, as steam together with the flue gas, leaves the power plant. According to that method, the heat required for the vaporization demands an unnecessarily high temperature level.
To improve the level of effectiveness of such power plants, drying the fuel prior to its combustion has already been suggested in indirectly heated fluidized bed dryers utilizing the vapor stream deriving from the drying process as a support medium for the fluidized bed. The disadvantage of such a procedure is that, based on the pure steam atmosphere in the dryer, i.e. of the high partial pressure of the steam, the heat required for the drying process must be produced at a relatively high temperature level. Besides, an additional expenditure in equipment is necessary, for example, for special parts such as a vapor cleaning device, evaporator, condenser and preparer for the vapor condensation which, even in a close inclusion into the generator process, cannot be reduced essentially.